Self-levelling support

ABSTRACT

A self-levelling support comprises a first stile ( 1 ) and a second stile ( 2 ), a first leg member ( 6 ) and a second leg member ( 7 ), each comprising an elongate element adapted to move longitudinally relative to one of the stiles ( 1, 2 ), a spacer means ( 3 ) adapted to secure the stiles ( 1, 2 ) substantially parallel to each other, and a cross member ( 8 ) adapted to pivot about a pivot pin ( 9 ) acting in a guide ( 10 ) in the spacer means ( 3 ) substantially midway between the stiles ( 1, 2 ), the cross member being connected at each end to a respective portion of the leg members, angular movement of the cross member about or with the pivot pin causing one leg member to move outwards relative to its respective stile whilst the other leg member moves inwards relative to its respective stile.

[0001] This invention relates to an improved self-levelling support foruse in combination with a ladder or platform to provide a stable footingon uneven ground, and to a ladder or platform incorporating such aself-levelling support.

[0002] Whilst ladders are easy to use on level ground, there is aproblem where a ladder is to be used on uneven ground. If the feet ofthe ladder are not in contact with ground of the same height, the ladderwill not stand vertically. A block could be placed beneath one of thefeet to make the ladder vertical, but this could lead to instabilityproblems.

[0003] In accordance with a first aspect, the invention provides aself-levelling support comprising:

[0004] a first stile and a second stile;

[0005] a first leg member and a second leg member, each comprising anelongate element adapted to move longitudinally relative to one of thestiles;

[0006] a spacer means adapted to secure the stiles in a fixed relationto each other; and

[0007] a cross member adapted to pivot about or with a pivot pin actingin a guide in the spacer means substantially midway between the stiles,the cross member being connected at each end to a respective portion ofthe leg members, angular movement of the cross member about or with thepivot pin causing one leg member to move outwards relative to itsrespective stile whilst the other leg member moves inwards relative toits respective stile.

[0008] By inwards we mean movement of the stile to shorten the overalllength of the leg and stile. By outwards we mean an increase in overalllength.

[0009] Each stile may comprise a hollow elongate member. In such aconstruction each leg member may comprise an elongate memberaccommodated within the respective stile and adapted to slide relativeto the stile. An aperture may be provided in each stile to allowconnection of each end of the cross-member to a leg member. Theapertures may each comprise an elongated slot. Alternatively, the legsmay also comprise hollow members which slide outside of the stiles.

[0010] The spacer may fix the stiles parallel to each other.

[0011] One or more of the leg members may be received within a footportion or pad which engages the ground. The foot portion or pad may beremovable and serve to increase the cross-sectional area of the leg thatengages the ground.

[0012] The spacer means may comprise a rung connecting the two stiles.It may further comprise one or more plates attached to the stiles and/orthe rung. Two plates are preferably provided, spaced apart by the stilesto define a cavity bounded by the stiles and the rung in which thecross-member is located. The plates are preferably welded to oppositesurfaces of the stiles and the rung. A cover may be provided whichbounds the remaining side of the cavity. The cover may locate betweenthe plates by, for example, forming a snap-fit between them. The cavityand the cross-member therein is thereby protected from dirt or otherforeign particles.

[0013] The guide in which the pivot pin is adapted to rotate maycomprise an elongate vertical slot. The pivot pin may be adapted to moveup and down along the slot as well as rotate. The guide may be providedin the or each plate of the spacer means. The or each slot may beprovided with a cap.

[0014] The pivot pin may comprise a solid tubular rod which extendsorthogonally through the cross-member. It may be retained in position inthe cross-member by a grub screw working in a threaded bore in thecross-member. Alternatively, the pivot pin may comprise a pair ofintegrally formed studs provided on opposing sides of the cross-member.

[0015] The cross-member may comprise an elongate beam fabricated from asheet of metal or a bar.

[0016] Fixing means may be provided on the cross-member and the spacermeans to retain the cross-member in a predetermined angular positionrelative to the stiles. The fixing means may come into operationautomatically when the predetermined angular position is obtained. Thefixing means may come into operation automatically when theself-levelling support is used with the cross-member at thepredetermined angular position.

[0017] The fixing means may comprise a toothed crescent portion providedon an upper face (or lower face) of the cross member which is adapted tomesh with one or more protrusions or teeth provided on the spacer means,when the pivot pin is at an upper end of the slot or slots in the spacermeans.

[0018] The protrusions on the spacer means may comprise a crescent ofconcave form of teeth complementary to the crescent of teeth on thecross-member. The arrangement may be such that more than one tooth onthe cross-member engages with more than one tooth on the spacer meansregardless of angular orientation of the cross member when the pivot pinis at the upper end of the slot or slots. This provides more strengththan a single meshed tooth. Preferably, seven teeth of the cross-memberengage with the teeth provided on the spacer means when the fixing meansis in operation.

[0019] All component parts on the support may be manufactured from steelor aluminium and may be welded or bolted or perhaps glued together.

[0020] According to a second aspect, the invention provides a ladder orframe including a support in accordance with the first aspect of theinvention. The ladder or frame may be attached to the stiles, or theself-levelling support may be formed as part of the ladder or frame.

[0021] The ladder may comprise two opposite stiles connected by rungs,and the base of the stiles of the ladder may be connected to orotherwise co-operate with the stiles of the support. They may engage atleast partially within the stiles of the support.

[0022] There will now be described, by way of example only, oneembodiment of the present invention with reference to the accompanyingdrawings in which:

[0023]FIG. 1 is a partially cut-away view of a support frame positionedon an uneven ground;

[0024]FIG. 2 is a similar partially cut-away view to FIG. 1 with theframe positioned above a level ground and the weight of the framepartially supported before dropping into position; and

[0025]FIG. 3 is a side view of the frame of FIGS. 1 and 2 showing thegrub screw locating the pivot pin in the cross member.

[0026]FIG. 1 shows a first embodiment of the invention.

[0027] The self-levelling platform comprises a pair of spaced apartelongate stiles 1, 2. The stiles are connected by a rung 3 and a frontand back support plate 4, 5 fastened by welding along three sides ontothe front and back of the stiles and the rung to define a cavity boundedby the stiles and the rung 3.

[0028] Each stile has a hollow tubular cross section (or box-like crosssection) over at least its lower portion. An adjustable leg member 6, 7comprising an elongate member is provided within each hollow stile. Thestiles allow the leg member to slide up and down within them so that theamount of leg member protruding from the bottom of each stile can bevaried. A rubber foot (not shown) may be provided on the lower end ofeach leg member.

[0029] Of course, in an alternative the stiles may be located withinhollow legs rather than outside of the legs.

[0030] An elongate rotatable cross-member 8 is provided which has acentrally located pivot pin 9 extending through an elongate slot 10provided in the centre of each of the front and back plates midwaybetween the two stiles.

[0031] The cross member is free to rotate with the pivot pin in a planecontaining the stiles and the rung. It can also translate upwardsrelative to the stiles as the pin moves in the elongate slots whichextend parallel to the stiles of the support. A grub screw 11 (seen inFIG. 3) holds the pivot pin 9 onto the cross-member 8. A cap (not shown)is provided over the slot 10.

[0032] The cross-member is connected at each end to an uppermost end ofa leg member. A transverse pin 12 engages with an elongate slot 20 inthe end of the leg member to provide a small amount of free playorthogonal to the main axis of the leg member. An elongate slot (notshown) is provided in each stile to allow its respective leg member toslide up and down within it.

[0033] A convex toothed crescent portion 21 of constant radius isprovided on the top face of the cross-member 8 having a centreco-incident with the central axis of the pivot pin and hence the axis ofrotation of the cross-member 8.

[0034] A concave toothed crescent portion 22 is provided on theunderside of the rung 3 facing the convex crescent portion 21 on thecross member when the cross member 8 is in a horizontal position. Theconcave toothed portion 22 is fixed by welding to the rung 3. so thatwhen the pivot pin on the cross-member is moved upwards to the top ofthe slot 10, one or more teeth on the cross-member engage one or moreteeth of the concave crescent portion 22 to prevent further rotation ofthe cross member. Furthermore, the position of the convex toothedcrescent portion 21 is such that when the pivot pin 9 is at the bottomof the slot 10 the teeth do not mesh and the cross-member 8 is free torotate. For all angular positions of the cross-member, seven teeth ofthe concave toothed crescent portion 22 mesh with seven teeth on theconvex toothed crescent portion 21 when the pivot pin is at the top ofthe slot 10.

[0035] The arrangement is such that when the support is held clear of asurface, the weight of the leg members acting on the end of thecross-member moves the pivot pin to the bottom of the slots in theplates so that the cross-member is free to rotate. If the leg membersare substantially identical in weight, they will hang from thecross-member to protrude from the stiles by equal amounts. As thesupport is lowered onto a surface of uneven height, one foot willcontact the ground first and the leg member will be pushed up into itsrespective stile as the support is lowered further. The cross-member 8will then rotate which will cause the other foot to move downwards outof its respective stile to contact the ground.

[0036] Eventually, on continued downwards movement of the support, bothfeet will contact the ground. On further downward movement of thesupport, the cross-member is pushed upwards by the leg members moving inparallel into the stiles, moving the pivot pin to the top of the slotsand causing one or more of the teeth of the two crescents to meshtogether. The length of each protruding portion of leg member is thenfixed. The weight of the support and any ladder or frame thereon causesthe cross-member to stay locked.

[0037] The elongate slot provided in each stile extends to the bottom ofeach stile. In this way, if the grub screw 11 is removed, allowingremoval of the pilot pin 9, the cross-member 8 together with the legmembers 6, 7 may be removed from the support, for inspection,maintenance or replacement of.these components.

[0038] In a refinement, an opening in a wall of at least one of thestiles may allow a lock pin to be inserted into one of a plurality ofreceiving holes (not shown) in the leg member to lock the leg member inposition. Thus, lifting of the platform will not upset the position ofthe legs once it has been set and the pin inserted

[0039]FIG. 2 shows the platform in a position where it is being loweredonto a flat surface. Further lowering of the platform will cause theteeth on the two crescents to inter mesh.

[0040]FIG. 1 show the platform in position on an uneven ground with thecross-member locked in place under the weight of the stiles and a load2F acting down upon the stiles.

1. A self-leveling support comprising: a first stile and a second stile;a first leg member and a second leg member, each comprising an elongateelement adapted to move longitudinally relative to one of the stiles; aspacer means adapted to secure the stiles in a fixed relation to eachother; and a cross member adapted to pivot about a pivot pin acting in aguide in the spacer means substantially midway between the stiles, thecross member being connected at each end to a respective portion of theleg members, angular movement of the cross member about the pivot pincausing one leg member to move outwards relative to its respective stilewhilst the other leg member moves inwards relative to its respectivestile.
 2. A self-leveling support according to claim 1 in which eachstile comprises a hollow elongate member and each leg member comprisesan elongate member accommodated within the respective stile and adaptedto slide relative to the stile.
 3. A self-levelling support according toclaim 1 or claim 2 in which an aperture is provided in each stile toallow connection of each end of the cross-member to a leg member.
 4. Aself-levelling support according to claim 3 in which the apertures eachcomprise an elongated slot.
 5. A self-levelling support according to anypreceding claim in which one or more of the leg members is receivedwithin a foot portion or pad which engages the ground.
 6. Aself-levelling support according to any preceding claim in which thespacer means comprises a rung connecting the two stiles.
 7. Aself-levelling support according to any preceding claim in which theguide in which the pivot pin is adapted to rotate comprises an elongatevertical slot.
 8. A self-levelling support according to claim 7 in whichthe pivot pin is adapted to move up and down along the slot as well asrotate.
 9. A self-levelling support according to any preceding claim inwhich the pivot pin comprises a solid tubular rod which extendsorthogonally through the cross-member.
 10. A self-levelling supportaccording to any preceding claim in which a fixing means is provided onthe cross-member and the spacer means to retain the cross-member in apredetermined angular position relative to the stiles when thepredetermined angular position is obtained.
 11. A self-levelling supportaccording to claim 10 in which the fixing means comprises a toothedcrescent portion provided on an upper face (or lower face) of thecross-member which is adapted to mesh with one or more protrusions orteeth provided on the spacer means, when the pivot pin is at an upperend of the slot or slots in the spacer means.
 12. A self-levellingsupport according to claim 11 in which the protrusions on the spacermeans comprise a crescent of concave form of teeth complementary to thecrescent of teeth on the cross-member.
 13. A ladder or frame including asupport in accordance with any one of claims 1 to
 12. 14. A ladder orframe according to claim 13 in which the legs of the ladder or frameco-operate with the stiles of the support.